All-Optical Wavelength Converter Based On Periodically Poled MgO:LiNbO₃

In this thesis, we investigate the fabrication and the second order nonlinear optical performance of periodically poled MgO:LiNbO3 (PPMgLN) theoretically and experimentally. The research focuses on the fabrication process, characteristics of broadband second-harmonic generation (SHG), effect of MgO doping on PPLN for femtosecond pulse SHG, and characteristics of all-optical wavelength converter.First, the fabrication technology for PPMgLN at room temperature is studied. Based on thorough understanding of the theory on micro-mechanism of poling process, we discuss the parameters of the poling process in details. Then we investigate several key factors which determine the poling result, including uniformity and contrast of electrical field, damage of the crystal samples and the leakage current.We investigate type I QPM broadband SHG in congruent PPLN, 5mol% and 7mol% PPMgLN at communication band. The relations between wavelength and grating period, sample temperature, incident degree are studied respectively. The two peaks phenomenon in broadband SHG is explained. Moreover, we study the effect of MgO doping in PPLN for femtosecond QPM SHG and provide the parameters for femtosecond laser pulses SHG in the three crystals.For the first time, we experimentally demonstrate flexible wavelength conversion, in which the input signals can be freely converted to output wavelengths through widely and arbitrarily tuning the pump wavelength within a broad second harmonic (SH) bandwidth up to 25 nm. The scheme is based on the cascadedχ(2) process in a 20-mm PPMgLN. Also, wavelength broadcasting can be performed by simultaneous use of multiple pumps with wavelengths located in the broad SH bandwidth.